Role of tungsten modifiers in bimetallic catalysts for enhanced hydrodeoxygenation activity and selectivity

Abstract

Bimetallic catalysts consisting of a noble metal and an oxophilic modifier have shown promise for upgrading lignin-derived molecules through hydrodeoxygenation (HDO). However, the mechanism of cooperation between the metals is not well understood currently. In this study, we investigated the HDO of gas-phase benzyl alcohol on W-modified Pt/Al₂O₃ catalysts. Our results show that bimetallic catalysts with an intermediate W loading have enhanced activity and selectivity for HDO compared to a baseline, monometallic Pt/Al₂O₃ catalyst. Characterization of the active site through CO chemisorption and CO diffuse-reflectance infrared spectroscopy suggests that decarbonylation is suppressed on bimetallic catalysts through site blocking and electronic effects. Based on results from X-ray photoelectron spectroscopy and titration with bases, enhancements in HDO activity were attributed to new active sites in the form of Brønsted acid centers on partially reduced WO_x generated through a bifunctional H₂ spillover interaction with Pt.